Alloy



Patented Aug. 16, 1938 PATENT OFFICE ALLOY Anthony de Golyer, New York,N. Y.

No Drawing. Application May 19, 1937, Serial No. 143,469 v 1 Claim.

The present invention relates to a new and useful alloy containingboron, zirconium, chromium and cobalt, which is characterized by beingresponsive to thermal treatment for the 5' improvement of physicalproperties. This application is a continuation in part of my copendingapplication Serial No. 721,771 filed April 21, 1934.

An object of the present invention is to provide an alloy especiallyadapted for use as metal cutting tools, the cutting efficiency of whichis superior to that of heretofore known high speed Y tools and otheralloys. A further object is to provide analloy which is free from, orsubstanlo tially free from, carbon, and which is readily amenable tothermal treatment by means of which the hardness, cutting efliciency andother physical properties and characteristics can be accuratelycontrolled over a comparatively wide range.

I have found through experiment that by alloying or otherwise intimatelycombining boron, zirconium, chromium and cobalt within the range ofboron 0.50% to 4%, zirconium 0.25% to 5%, chromium 1% to 17% and cobaltsubstantially the balance, that I obtain metallic compositions which arereadily responsive to thermal treatment by means of which the physicalproperties and characteristics can be developed and controlled.

Alloys of this invention may be used in the cast condition for certainpurposes, but approximatemaximum values of hardness, resistance toimpact and certain other important physical properties can be developedonly through thermal treatment, or through mechanical working andthermal treatment. Bodies of the alloy which have been subjected to suchtreatment are particularly valuable for use as tools, dies,

40 and the like for the-cutting .or mechanical working of metals, aswell as for many other industrial uses.

Numerous metallic compositions have heretofore been proposed asimprovements on the known types of high speed tool steel, but all ofsuch proposed compositions have disadvantages which render themunsuitable for general application as metal cutting or forming tools.One

disadvantage of such compositions is that nonev treatment for thedevelopment of precipitation hardening, often referred to as agehardening.

I prefer to subject the alloy to thermal treatment before using it formetal cutting tools,'dies, etc. 7 I have found that both the cast andforged mate- 5 rials are responsive to thermal treatment. As anillustration, cast bodies of this alloy may have a hardness of from 52to 58 on the Rockwell C scale and by subjecting the material to suitablethermal treatment, such as heating to a tem- 1o perature higher thanapproximately 1000" C., followed by rapid quenching, the hardness may belowered to an approximate range of from'36' to .44 Rockwell C. The alloycan subsequently be subjected to a second thermal treatment, such 15 asheating to a temperature lower than 1000 C. for a period of one hour ormore, followed by cooling at a normal rate, by which the hardness can beincreased to from approximately 58 to 66 Rockwell C. valuable for manyindustrial uses.

An important property of the alloy is that virtually all of the maximumhardness, developed by thermal treatment, is retained when the alloy issubjected to temperatures between 500 and 2a The more importantdistinctive advantages 5 are apparently due to the presence. ofappreciable amounts of boron in the composition, in conjunction with theother components, within the percentages specified herein.

Specific examples of composition within the 40 scope of the presentinvention which I have found well adapted for numerous industrialapplications are of the following: boron 1.75%, zlrconium 4.75%,chromium.7.50 cobalt substantially the balance; boron 1.95%, zirconium45 0.75%, chromium 15%, cobalt substantially the balance;. boron 2.30%,zirconium 2%, chromium 12%, cobalt substantially the balance.

An objective of the present invention is to provide an alloy having highhardness, advanta- 60 geous metal cutting properties, etc., which isfree from, or substantially free from, carbon, and thus eliminate all ofthe serious disadvantages associated with carbon containing alloys orcompositions intended for metal cutting tools, etc. Al-

'In the latter condition the alloy is 20 though I prefer to have thealloys entirely free from carbon, in many instances I have found carbonpresent in the nature of an impurity incidental to manufacture. It' isimportant, however. to restrict the carbon content to a maximum 0! about0.15%, as I have found that the presence of higher percentages of thiselement not only embrittle the alloy, but also inhibit or retard thedesired or necessary reactions during thermal treatment. The presence ofappreciable amounts of carbon decreases the red hardness of the alloy;1-. e., hardness at temperatures oi approximately 550 C. and higher.

My investigations indicate that the preferred structure of a body of thepresent alloy, particularly after thermal treatment, comprises at leasttwo-principal constituents; one, a relatively hard lntermetallicjcompound of boron with one or more of the other essential components;and,

two, a solid solution of two or more or the essentlal components whichhas a lower degree of hardness and functions as a matrix. The ratio ofthe constituents as well as the ratio oi particle size in any particularbody or the alloy may be accurately controlled and fixed over a widerange I by means of thermal treatment or mechanical working and thermaltreatment.

By reason of the combined advantageous physical propertiesand-characteristics'possessed by the alloy 01' the present invention,tools and other articles composed oi! this alloy may be operatedeiliciently and economically under conditions which are impossible oruneconomical with tools, etc., composed of heretofore ,khow'n alloys ormetallic compositions.

By the term the balance substantially cobalt" or the "balance cobalt" inthe foregoing and in the following claim, I intend that the alloy of thepresent invention comprises boron, zirconium,

and chromium within the percentaae limits specified, with the remaindercobalt, except for inei'iectual amounts of impurities which may bepresent incidental to manufacture.

I claim:

' A precipitation hardened. alloy containing boron 0.50% .to 4%,zirconium-0.25% to--5%, chromium 1% to 17%, the balance cobalt.

ANTHONY G. or GOLYER.

